CN118265588A - Arc welding method and arc welding device - Google Patents

Abstract

The second member (W2) has a larger heat capacity than the first member (W1). Welding is performed while a welding gun (11) is oscillated so as to traverse a boundary position (Wb) between the first member (W1) and the second member (W2). During the swinging motion, a first welding is performed on the first member (W1), and a second welding is performed on the second member (W2). In the first welding, at least short-circuit welding is performed. In the second welding, at least pulse welding is performed.

Description

Arc welding method and arc welding device

Technical Field

The present invention relates to an arc welding method and an arc welding apparatus.

Background

Patent document 1 discloses consumable electrode arc welding in which pulse welding and short-circuit welding are alternately repeated, wherein a welding current immediately before a transition from pulse welding to short-circuit welding is made lower than a base current in a pulse.

Patent document 1: international publication No. 2016/059805

Disclosure of Invention

Technical problem to be solved by the invention

In the case of arc welding two members having different heat capacities due to different plate thicknesses and materials, for example, if pulse welding with high heat input is performed to members having a relatively thin plate thickness, the members may burn through to cause poor joining.

The present invention has been made to solve the above-mentioned problems, and has an object of: improving the quality of the joint between the components having different heat capacities.

Technical solution for solving the technical problems

A first aspect relates to an arc welding method of feeding a welding wire as a consumable electrode toward a welding object having a first member and a second member having a larger heat capacity than the first member, and generating an arc between the welding wire and the welding object to perform welding, the arc welding method including: a step of welding while swinging the welding gun so as to alternately cross the boundary position between the first member and the second member a plurality of times; and switching welding operations during the swinging operations so as to perform a first welding of the first member, wherein at least a short-circuit welding is performed, and a second welding of the second member, wherein at least a pulse welding is performed.

In a first aspect, the heat capacity of the second component is greater than the heat capacity of the first component. Welding is performed while the welding gun is oscillated so as to alternately cross the boundary position between the first member and the second member a plurality of times. During the swinging motion, a first weld is performed to the first component and a second weld is performed to the second component. In the first welding, at least short-circuit welding is performed. In the second welding, at least pulse welding is performed.

In this way, the joining quality between the members having different heat capacities can be improved. Specifically, by short-circuit welding with low heat input to the first member having a small heat capacity, the first member can be suppressed from being burned through. In addition, by pulse welding with high heat input to the second member having a large heat capacity, occurrence of insufficient penetration can be suppressed.

By switching the welding method in synchronization with the swinging operation of the welding gun in this manner, it is possible to provide an appropriate heat input when welding objects having different thicknesses or objects having a complicated shape. As a result, burn-through does not occur, and a desired penetration can be obtained.

In addition, in the direct current welding in which the pulse welding current alternately changes between the peak current and the base current flows into the welding wire and the welding object, it is not necessary to provide an additional alternating current unit as in the alternating current welding, and the cost of the whole device can be reduced.

A second aspect is the arc welding method according to the first aspect, wherein, in at least one of the first welding and the second welding, a third welding is performed in which a short-circuit welding period during which the short-circuit welding is performed and a pulse welding period during which the pulse welding is performed are alternately switched a plurality of times.

In a second aspect, in at least one of the first welding and the second welding, a third welding is performed. The third weld has an intermediate property that the heat input is higher than the short circuit weld and the heat input is lower than the pulse weld. By performing the third welding, a rapid change in heat input when the welding current is changed can be suppressed.

A third aspect is based on the arc welding method of the second aspect, including: a step of making a ratio of the short-circuit welding period during which the short-circuit welding is performed in the third welding larger than a ratio of the pulse welding period during which the pulse welding is performed when the third welding is performed in the first welding; and a step of, when the third welding is performed in the second welding, making a ratio of the pulse welding period during which the pulse welding is performed in the third welding larger than a ratio of the short-circuit welding period during which the short-circuit welding is performed.

In a third aspect, a short circuit welding period during which short circuit welding is performed and a pulse welding period during which pulse welding is performed are included. When the third welding is performed on the first member having the smaller heat capacity, the ratio of the short-circuit welding period during which the short-circuit welding having the lower heat input than the pulse welding is performed is made larger. In addition, when the third welding is performed on the second member having a large heat capacity, the ratio of the pulse welding period of the pulse welding in which the high heat input is performed is made large. In this way, the third welding can be performed under appropriate conditions.

A fourth aspect is based on the arc welding method of the second or third aspect, comprising: in the second welding, before the welding gun traverses the boundary position from the second member toward the first member, switching is performed in the order of the pulse welding, the third welding, and the short-circuit welding.

In a fourth aspect, the transition to short circuit welding is made gradually before moving the welding gun from the second part having the larger heat capacity toward the first part having the smaller heat capacity. Thus, the pulse welding, the third welding, and the short-circuit welding can be combined, and abrupt changes in heat input can be suppressed.

A fifth aspect is based on the arc welding method of any one of the second to fourth aspects, comprising: in the third welding, a step of gradually changing at least one of the number of pulses in the pulse welding and the number of shorts in the short-circuit welding.

In the fifth aspect, by gradually changing at least one of the number of pulses in pulse welding and the number of shorts in short-circuit welding, abrupt changes in heat input can be suppressed.

A sixth aspect is based on the arc welding method of any one of the first to fifth aspects, wherein a welding current applied when the welding torch traverses the boundary position from the first member toward the second member is greater than a welding current applied before the welding torch traverses the boundary position.

In the sixth aspect, the welding current applied when crossing the boundary position is the average welding current which is the average current of the moving average of the welding currents, and by making the average welding current applied to the welding wire when crossing the boundary position larger, the feeding amount of the welding wire at the boundary position can be increased, and the pile height of the welding bead can be ensured. Thus, the step generated at the junction between the thin plate and the thick plate can be buried.

A seventh aspect is based on the arc welding method of any one of the second to sixth aspects, wherein when the welding gun traverses the boundary position from the second member toward the first member, a ratio of a number of short circuits of the short circuit welding in the third welding is larger than a ratio of a number of short circuits of the short circuit welding in the third welding before the welding gun traverses the boundary position.

In the seventh aspect, the ratio of the number of short circuits when the welding gun crosses the boundary position is made larger than the ratio of the number of short circuits before the welding gun crosses the boundary position, and the ratio of the number of short circuits is increased from before the welding gun crosses the boundary position to when the welding gun crosses the boundary position, whereby the amount of piling up of the weld bead at the boundary position can be ensured in the low heat input state. Thus, the step generated at the junction between the thin plate and the thick plate can be buried.

An eighth aspect is the arc welding method according to any one of the first to seventh aspects, wherein the swinging motion is a spiral swinging motion that moves along a spiral trajectory, and a distance from a center position of the spiral trajectory to a spiral trajectory on a rear side in a welding direction is shorter than a distance from the center position to a spiral trajectory on a front side in the welding direction at the boundary position.

In the eighth aspect, the distance from the spiral center position to the spiral track on the rear side in the welding direction at the boundary position is made shorter than the distance from the spiral center position to the spiral track on the front side in the welding direction at the boundary position, whereby penetration can be suppressed and the amount of stacked weld beads can be ensured.

A ninth aspect is the arc welding method of any one of the first to eighth aspects, wherein the welding wire is fed at a constant speed in at least one of the first welding and the second welding.

In a ninth aspect, the welding wire is fed at a constant speed.

A tenth aspect is the arc welding method of any one of the first to eighth aspects, wherein, in at least one of the first welding and the second welding, the forward feeding and the reverse feeding of the welding wire are periodically and repeatedly alternated to feed the welding wire.

In the tenth aspect, the forward feeding and the reverse feeding of the welding wire are periodically and repeatedly alternated to feed the welding wire.

In this way, the heat input applied to the welding object can be reduced. Specifically, when the welding wire is short-circuited to the welding object, the welding voltage is close to 0V, and the heat input amount per unit time, that is, the heat input amount, is extremely small.

Here, when the welding wire is fed forward and backward, the welding wire is fed backward when the welding wire is short-circuited to the welding object, and when an arc is generated between the welding wire and the welding object, the welding wire is accelerated to be fed forward, so that the number of times of short-circuiting is dramatically increased compared with the case where the welding wire is fed constantly to the welding object. In this way, the effect of periodically cooling the welding object can be obtained.

Further, by feeding the welding wire forward and backward at the time of short circuit, the spatter generation can be suppressed, and the welding quality can be improved.

An eleventh aspect is the arc welding method according to any one of the second to tenth aspects, wherein the swinging motion is a spiral swinging motion that moves along a spiral trajectory, and the third welding is performed, and in the third welding, the short-circuit welding period during which the short-circuit welding is performed and the pulse welding period during which the pulse welding is performed are switched a plurality of times, and a ratio of the pulse welding period is made larger than a ratio of the short-circuit welding period in a front side of a welding direction and a ratio of the short-circuit welding period is made larger than a ratio of the pulse welding period in a rear side of the welding direction, based on a center position of the spiral trajectory.

In the eleventh aspect, the molten pool is formed by making the ratio of the pulse welding period of the pulse welding in which the high heat input is performed larger in front of the welding direction, and the molten pool is cooled by making the ratio of the short circuit welding period of the short circuit welding in which the heat input is lower than the pulse welding larger in rear of the welding direction. Thus, the penetration of the welding object can be suppressed, and the scale pattern of the weld bead can be made clear.

A twelfth aspect relates to an arc welding apparatus configured to perform welding by feeding a welding wire as a consumable electrode toward a welding object having a first member and a second member having a heat capacity larger than that of the first member, and to perform welding by generating an arc between the welding wire and the welding object, the arc welding apparatus including a welding unit configured to perform welding while swinging a welding gun so as to alternately traverse a boundary position between the first member and the second member a plurality of times, and a control unit configured to control an operation of the welding unit, wherein the control unit controls the operation of the welding unit so as to perform first welding on the first member and perform second welding on the second member during the swinging operation, and wherein at least short-circuit welding is performed during the second welding, and at least pulse welding is performed during the first welding.

In the twelfth aspect, the heat input of the short-circuit welding is lower than that of the pulse welding, and by performing the short-circuit welding with low heat input to the first member with small heat capacity, burn-through of the first member can be suppressed. In addition, by pulse welding with high heat input to the second member having a large heat capacity, occurrence of insufficient penetration can be suppressed.

Effects of the invention

According to aspects of the present disclosure, the joining quality between the components having different heat capacities can be improved.

Drawings

Fig. 1 is a schematic configuration diagram of an arc welding apparatus according to the present embodiment;

FIG. 2 is a graph showing waveforms and droplet transitions of welding current, welding voltage, and wire feed speed in a short circuit weld;

FIG. 3 is a graph showing waveforms of welding current, welding voltage, and wire feed speed and droplet transition states in pulse welding;

FIG. 4 is a graph showing waveforms of welding current, welding voltage, and wire feed speed in pulse hybrid welding;

fig. 5 is a side sectional view showing a state in which arc welding is performed while performing a spiral swing motion;

fig. 6 is a perspective view showing a state in which arc welding is performed while performing a spiral swing motion;

Fig. 7 is a perspective view illustrating the timing of switching short-circuit welding, pulse welding, and pulse hybrid welding;

fig. 8 is a diagram illustrating a relationship between a welding speed and a bead appearance when pulse hybrid welding is performed without performing a spiral swing motion;

FIG. 9 is a view illustrating a relationship between a welding speed and a bead appearance when pulse hybrid welding is performed during a spiral swing motion;

fig. 10 is a diagram showing a trajectory of a spiral swing motion according to a modification of the present embodiment.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or uses.

As shown in fig. 1, the arc welding apparatus 1 welds a welding object W by generating an arc 16 between a welding wire 15 as a consumable electrode and the welding object W.

The arc welding apparatus 1 includes a welding unit 10 and a control unit 30. The welding unit 10 includes a welding gun 11, a feed motor 12, a robot 13, and a power conversion unit 20. The feed motor 12 feeds the welding wire 15 to the welding gun 11 at a prescribed feed speed.

The robot 13 has a plurality of joints. A welding gun 11 is attached to a distal end portion of the robot 13. The robot 13 moves the welding gun 11 with respect to the position of the welding object W. The robot 13 causes the welding torch 11 to perform a spiral swinging motion along a spiral trajectory, which will be described in detail later.

The power conversion unit 20 includes a primary-side rectifying unit 21, a switching unit 22, a main transformer 23, a secondary-side rectifying unit 24, a reactor 25, a voltage detection unit 26, and a current detection unit 27.

The primary-side rectifying unit 21 rectifies and outputs the output of the input power source 5. The switching section 22 converts the dc output from the primary-side rectifying section 21 into ac. The switching unit 22 controls a welding output including a welding current and a welding voltage.

The main transformer 23 converts the ac voltage output from the switching unit 22. The output of the main transformer 23 is output as a welding output through the secondary side rectifying unit 24 and the reactor 25. The secondary-side rectifying unit 24 rectifies the secondary-side output of the main transformer 23. The voltage detection unit 26 detects the welding voltage V. The current detecting unit 27 detects the welding current I.

The control unit 30 includes a driving unit 31, a short-circuit welding control unit 33, a pulse welding control unit 32, a pulse hybrid welding control unit 34, a welding condition setting unit 35, a storage unit 36, a feed speed control unit 37, a first switching unit 38, a second switching unit 39, and a robot control unit 40. The short-circuit welding control unit 33 performs control for the first welding including the short-circuit welding, the pulse welding control unit 32 performs control for the second welding including the pulse welding, and the pulse hybrid welding control unit 34 performs control for the third welding described later.

The driving unit 31 controls the switching unit 22. The pulse welding control unit 32 performs control for pulse welding. The short-circuit welding control unit 33 performs control for short-circuit welding. The pulse hybrid welding control unit 34 performs control for the third welding.

Here, the third welding is a welding method in which short-circuit welding and pulse welding are alternately repeated a predetermined number of times. In the present embodiment, the third welding is defined as "pulse hybrid welding", and in the following description, description will be made using this expression.

In the pulse hybrid welding, the feeding of the welding wire 15 is preferably: the welding wire 15 is fed substantially forward and backward in the short circuit welding, and the welding wire 15 is fed substantially at a constant speed in the pulse welding. However, this method is not limited thereto. For example, as described later with reference to fig. 3, the feeding speed of the welding wire 15 may be changed during pulse welding. In short-circuit welding, the wire 15 may be fed at a constant speed.

In the pulse hybrid welding, the number of pulses in the pulse welding and the number of short circuits in the short circuit welding may be gradually changed. By gradually changing at least one of the number of pulses in pulse welding and the number of shorts in short-circuit welding, abrupt changes in heat input can be suppressed. For example, in fig. 4 described later, the number of pulses is set to six and the number of short circuits is set to three to repeat the process, but the number of pulses may be changed to three and the number of short circuits may be changed to six to repeat the process a plurality of times. The pulse number and the short circuit number are only examples, and are not limited thereto.

The timing of gradually changing the number of pulses and the number of short circuits may be, for example, the timing of gradually changing the number of pulses and the number of short circuits each time a predetermined welding distance is elapsed, each time a predetermined welding time is elapsed, or at each preset teaching point.

The welding condition setting unit 35 sets welding conditions including a welding current and a welding voltage. Specifically, the welding condition setting unit 35 sets a set welding current for performing welding, a set welding voltage for performing welding, a feeding speed of the wire 15, a kind of shielding gas, a material of the wire 15, a diameter of the wire 15, a period and a number of pulse outputs of pulse welding, a period and a number of short-circuit outputs of short-circuit welding, and the like.

The shielding gas is used according to the material and the purpose of the welding wire. For example, in welding aluminum alloys, argon (Ar) is used. MIG gas (98% ar+2% o 2) was used in welding stainless steel. In welding low carbon steel, MAG gas (80% Ar+20% CO 2) was used. In welding low carbon steel, carbon dioxide (CO 2) is used if cost is important. The kind of the shielding gas is only one example.

The storage unit 36 stores a predetermined threshold value. The threshold value stored in the storage unit 36 is a threshold value of a welding parameter related to heat input applied to the welding object W, and is a welding current, a welding voltage, a feeding speed, and the like. The storage unit 36 outputs a welding operation, an appropriate control value, a feeding speed of the welding wire 15, and the like, which are stored in advance, based on the output from the welding condition setting unit 35.

The feed speed control unit 37 controls the feed speed of the welding wire 15 according to the set current of the welding current set by the welding condition setting unit 35. Here, there is a correlation between the feed speed and the welding current. More specifically, there is a correlation between an average welding speed (also referred to as a feed amount) as a moving average value and an average current (also referred to as a set current) as an average current as a moving average value.

The first switching unit 38 outputs a signal for welding output of any one of the pulse welding control unit 32, the short-circuit welding control unit 33, and the pulse hybrid welding control unit 34, based on the output of the storage unit 36.

The second switching unit 39 selects the output of the feed speed of any one of the pulse welding control unit 32, the short-circuit welding control unit 33, and the pulse hybrid welding control unit 34 based on the output of the storage unit 36.

The robot control unit 40 controls the operation of the robot 13. The robot control unit 40 sends a current command to a motor (not shown) for each axis of the robot 13, thereby moving the welding gun 11 in the welding direction of the welding object W.

< Method of controlling arc welding apparatus >

Next, the operation of the arc welding apparatus 1 will be described. The arc welding apparatus 1 supplies a shielding gas from a gas supply port, not shown, to isolate a welding portion of the welding object W from the outside air, and supplies a current between the welding wire 15 and the welding object W.

In this way, an arc 16 is generated between the welding wire 15 and the welding object W, and the tip portion of the welding wire 15 and a part of the welding object W are melted by the heat of the arc 16. The melted welding wire 15 forms a droplet and drops on the welding object W, and forms a molten pool together with a part of the welding object W melted by the heat of the arc 16.

The welding torch 11 moves in the welding direction while performing a spiral swinging motion with respect to the welding object W. As the welding gun 11 moves, a weld bead is formed on the welding object W, and the welding object W is welded.

The arc welding apparatus 1 performs welding of the welding object W while switching between short-circuit welding, pulse welding, and pulse hybrid welding.

Fig. 2 is a diagram showing waveforms of welding current, welding voltage, and wire feed speed and droplet transition states in short-circuit welding. In fig. 2, the vertical axis represents welding current I, welding voltage V, and feed speed WF, and the horizontal axis represents time.

In the short-circuit welding, the welding current I is controlled so as to alternate between a short-circuit period in which the welding wire 15 contacts the welding target W to short-circuit, and an arc period in which the arc 16 is generated between the welding wire 15 and the welding target W. During the short-circuiting, the welding wire 15 is short-circuited with the welding object W. During the arc, an arc 16 is generated between the welding wire 15 and the welding object W. In the short circuit welding, for example, a welding current of 100A is applied to the wire 15.

In fig. 2, P1 represents a time point at which a short circuit starts, and the short circuit current is gradually increased after a short circuit initial current is output for a predetermined time period from the time point P1 during a short circuit period from P1 to P2.

P2 indicates the time when the short-circuit state ends and the arc state occurs. During the arc from P2 to P3, a first welding current is output as a peak current immediately after the arc is generated, and then, a transition is made to a second welding current lower than the first welding current. The arc periods P2 to P3 are arc states in which an arc 16 is generated between the welding wire 15 and the welding target W. During this arc period, an arc 16 is generated between the welding wire 15 and the welding object W, and a droplet is formed at the tip end portion of the welding wire 15 by the heat of the arc 16, thereby melting a part of the welding object W.

P3 represents the time when the next short circuit occurs after P1, and the state at time P3 is the same as the state at time P1. The welding wire 15 contacts the welding object W to cause a short circuit, and a droplet formed at the tip end portion of the welding wire 15 during the arc is short-circuited and transited to the welding object W to form a molten pool to perform short-circuit welding.

In this way, the short-circuit welding periodically and repeatedly alternates the short-circuit period from P1 (P3) to P2 and the short-circuit period from P2 to P3.

In the example shown in fig. 2, wire feed control is performed in which forward feed and reverse feed are periodically and repeatedly alternated a plurality of times in a sinusoidal waveform having a waveform with a predetermined frequency and a predetermined velocity amplitude as a basic waveform. When the peak value is on the forward feed side, a short circuit occurs near the point P1, and when the peak value is on the reverse feed side, an arc occurs near the point P2. Further, when the peak value of the forward feed after the time P2 is set, the next short circuit occurs near the time P3.

As described above, P1 to P3 are set as one cycle of control, and the control of this cycle is repeated to perform welding.

Fig. 3 is a diagram showing waveforms of welding current, welding voltage, and wire feed speed and droplet transition states in pulse welding. In fig. 3, the vertical axis represents welding current I, welding voltage V, and feed speed WF, and the horizontal axis represents time. The pulse welding is welding in which a peak current IP and a base current IB are alternately applied repeatedly. In pulse welding, for example, a welding current of 200A is applied to the wire 15.

As shown in fig. 3, the arc welding apparatus 1 supplies a welding current I and a welding voltage V to a welding wire 15. The pulse waveform of welding current I includes a pulse rising period IPRT during which welding current I transitions from base current IB to peak current IP, a peak current period IPT during which welding current I is peak current IP, a pulse falling period IPFT during which welding current I transitions from peak current IP to base current IB, and a base current period IBT during which welding current I is base current IB.

The pulse rising period IPRT, the peak current period IPT, the pulse falling period IPFT, and the base current period IBT are sequentially and periodically repeated at the pulse frequency PHz, whereby a periodic droplet transition state can be obtained.

In the pulse rising period IPRT and the peak current period IPT, the feeding speed WF of the welding wire 15 is set to the first feeding speed WF1. During the pulse down period IPFT, the feed speed WF of the wire 15 is switched from the first feed speed WF1 to the second feed speed WF2.

The arc welding apparatus 1 generates an arc 16 between the welding wire 15 and the welding object W, and melts a part of the welding object W by forming a droplet at the tip end of the welding wire 15 by the heat of the arc 16.

The droplet formed at the tip end portion of the welding wire 15 moves from the tip end of the welding wire 15 to the welding object W due to the droplet transition, and adheres to the welding object W, thereby forming a molten pool on the welding object W. In this way, in pulse welding in which the peak current IP and the base current IB are alternately applied repeatedly, one pulse period 1/PHz including one peak current IP and one base current IB is set as one pulse unit, and one droplet is welded to one pulse of the welding object W in each pulse period, in other words, in each pulse having one peak current. In the droplet-free state after the droplet transition, the arc welding device 1 changes the arc length H of the arc 16 with respect to the reference arc length H1. Specifically, the arc welding apparatus 1 accelerates and decelerates the welding wire 15 during pulse welding.

In the example shown in fig. 3, at the beginning of the pulse down period IPFT, the feed speed WF of the wire 15 is switched from the first feed speed WF1 to the second feed speed WF2, and the wire 15 is accelerated. At time TP, a short circuit between wire 15 and welding object W is detected. During the period from time TP to time NP, the welding current IS increased to the current IS.

At time NP, the feeding speed WF of the wire 15 is switched from the second feeding speed WF2 to the third feeding speed WF3, and the wire 15 is decelerated.

When it IS detected at the time NP that a neck IS formed IN the droplet formed between the welding wire 15 and the welding object W, the welding current I sharply decreases from the current IS at the time NP toward the current IN (a current lower than the current IS).

The welding current I is maintained at the second current IN from the time NP to the time AP.

When a short-circuit break between the welding wire 15 and the welding object W is detected at the timing AP, the third feed speed WF3 of the welding wire 15 is switched to the first feed speed WF1.

In fig. 3, an example in which the feed speed WF of the wire 15 is changed during the pulse welding is described, but the feed speed WF of the wire 15 may be kept constant to perform the normal pulse welding one by one. In this case, at the time of droplet transition, the arc 16 is continuously generated by the peak current and the base current without causing a short circuit between the welding wire 15 and the welding object W, and the droplet formed on the tip of the welding wire 15 is separated from the tip of the welding wire 15 in the air and transits to the welding object W so that one droplet is transited to one pulse of the welding object W every time a pulse having one peak current is generated.

Fig. 4 is a graph showing waveforms of a welding current, a welding voltage, and a wire feed speed in pulse hybrid welding. The pulse hybrid welding is a welding in which a pulse welding period Tp in which pulse welding is alternately repeated and a short circuit welding period Ts in which short circuit welding is performed are repeated a plurality of times. Here, pulse hybrid welding, which is a combination of dc short-circuit welding and dc pulse welding, will be described as dc welding. In fig. 4, the vertical axis represents welding current I, welding voltage V, and feed speed WF, and the horizontal axis represents time.

During the pulse welding period Tp in which pulse welding is performed, the welding current I is controlled so that the welding current I flowing through the wire 15 forms a plurality of pulses in which the peak current Ip and the base current Ib repeatedly alternate.

In a short-circuit welding period Ts in which short-circuit welding is performed, a welding current I is controlled so that one or more short-circuit periods S in which the welding wire 15 and the welding target W are short-circuited and one or more arc periods a in which an arc 16 is generated between the welding wire 15 and the welding target W alternate.

The pulse welding period Tp and the short-circuit welding period Ts repeatedly alternate so that the pulse welding period Tp follows the short-circuit welding period Ts, and the short-circuit welding period Ts follows the pulse welding period Tp.

The pulse welding period Tp can be detected by detecting a case where the welding current I changes from a value greater than the preset threshold Is to a value less than the preset threshold Is, for example. The short-circuit welding period Ts can be detected by detecting a change in the welding voltage V from a value greater than a preset threshold value Vs to a value less than the preset threshold value Vs, for example.

The feed speed control unit 37 outputs a control output to the feed motor 12 so that the feed speed WF of the wire 15 is a preset feed speed during the pulse welding period Tp and the short-circuit welding period Ts. Thereby, during the pulse welding period Tp, the welding wire 15 is fed at the constant third feeding speed WF 3.

On the other hand, during the short-circuit welding period Ts, the feed rate WF of the welding wire 15 is changed in accordance with a periodic waveform having a predetermined amplitude and period. The feed speed WF shown in fig. 4 varies as a periodic waveform in accordance with a sine wave.

When the number of times of short-circuiting reaches the pulse start time Tps of the number of times preset by the welding condition setting unit 35, the short-circuiting is disconnected. The pulse start time Tps may be a time after the lapse of a time preset by the welding condition setting unit 35. A pulse welding period Tp during which pulse welding is started from the pulse start time Tps.

The pulse-hybrid welding control unit 34 starts the pulse welding period Tp and generates the first pulse of the plurality of pulses.

After the pulse start time Tps, the feed speed WF continues to vary according to the periodic waveform of the short-circuit welding period Ts, and in this state, the feed speed WF varies to the third feed speed WF3 of the welding wire 15 in the pulse welding period Tp preset by the welding condition setting unit 35, and when the feed speed WF reaches the third feed speed WF3 in the pulse welding period Tp, the feeding unit 14 feeds the welding wire 15 at the third feed speed WF 3.

Then, in the pulse welding period Tp, when the number of pulses reaches the number of times preset by the welding condition setting unit 35 or when the time preset by the welding condition setting unit 35 has elapsed, the pulse hybrid welding control unit 34 changes the welding current I to the current 13 different from the base value current Ib in the pulse after the last pulse is formed.

When the welding current I is changed to the current 13 after the last pulse is formed, the feeding speed WF is changed from the third feeding speed WF3 in the pulse welding period Tp to the forward feeding direction and the reverse feeding direction at the feeding switching time Tvs when the welding current I is the current 13, in accordance with the above-described periodic waveform.

In this way, welding is performed by feeding the welding wire 15 at the optimal feed speed WF in each mode while repeatedly alternating the pulse welding period Tp and the short-circuit welding period Ts under the set conditions.

In the present embodiment, the short-circuit welding, the pulse welding, and the pulse hybrid welding are switched according to the heat capacity of the welding target W.

Specifically, as shown in fig. 5 and 6, the welding object W has a first member W1 and a second member W2. The second member W2 has a thicker plate thickness than the first member W1. Therefore, the heat capacity of the second member W2 is larger than that of the first member W1. The first member W1 and the second member W2 are formed of, for example, aluminum. The first member W1 and the second member W2 are arranged in a state of abutting each other.

The position where the first member W1 abuts against the second member W2 is the boundary position Wb between the first member W1 and the second member W2. The arc welding apparatus 1 performs welding while causing the welding torch 11 to perform a spiral swing motion so as to alternately traverse the boundary position Wb between the first member W1 and the second member W2 a plurality of times.

Here, the spiral swing motion is the following motion: the welding torch 11 is moved along a spiral trajectory by moving the welding torch 11 along a circular trajectory while moving in the welding direction.

In the example shown in fig. 6, the welding wire 15 fed from the welding gun 11 is rotationally moved so as to rotate around the rotation center RC at a predetermined rotation frequency with a distance of a rotation radius r from the rotation center RC, which moves in the welding direction at the boundary position Wb between the first member W1 and the second member W2. The magnitude of the rotation radius r shown in fig. 6 is merely an example, and is not limited thereto. For example, in fig. 5 and 6, the welding gun 11 may be moved to a position where the welding wire 15 can be supplied to the upper surface of the second member W2.

The arc welding apparatus 1 switches the welding operation so that the first welding is performed on the first member W1 and the second welding is performed on the second member W2 during the spiral swing operation. The first weld includes at least a short circuit weld of low heat input. The second weld includes at least a pulse weld of high heat input. In at least one of the first welding and the second welding, a third welding is performed. The third welding is pulse hybrid welding in which short-circuit welding and pulse welding are alternately repeated a predetermined number of times.

Next, the timings of the switching short-circuit welding, the pulse welding, and the pulse hybrid welding will be described with reference to fig. 7.

As shown in fig. 7, the arc welding is performed in the welding direction while rotating clockwise around the rotation center RC, with the start position of the arc welding at the boundary position Wb between the first member W1 and the second member W2 being set to 0 °.

In fig. 7, a section of 20 ° to 160 ° is defined as a first section 41, a section of 160 ° to 190 ° is defined as a second section 42, a section of 190 ° to 350 ° is defined as a third section 43, and a section of 350 ° to 20 ° is defined as a fourth section 44. The angular range of each section is only an example.

In the first section 41, the first switching unit 38 performs short-circuit welding by selecting an output of the short-circuit welding control unit 33 suitable for the first member W1 having a small heat capacity in the first welding for welding the first member W1.

In the first section 41, the first switching unit 38 may select the output of the pulse hybrid welding control unit 34 after the start of the short-circuit welding, and perform the pulse hybrid welding. The pulse hybrid welding is a third welding in which a pulse welding period Tp in which pulse welding is alternately repeated and a short-circuit welding period Ts in which short-circuit welding is performed are repeated a plurality of times, and has an intermediate characteristic in that the heat input is higher than that of the short-circuit welding and lower than that of the pulse welding. By performing pulse hybrid welding, abrupt changes in heat input when the welding current is changed can be suppressed.

When the pulse hybrid welding is performed in the first welding, the control unit 30 controls the operation of the welding unit 10 so that the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed in the pulse hybrid welding is greater than the ratio of the pulse welding period Tp during which the pulse welding is performed. In this way, pulse hybrid welding can be performed under appropriate conditions. In the first welding, control may be performed so that only short-circuit welding is performed, and pulse hybrid welding is not performed. In the pulse hybrid welding, the number of pulses in the pulse welding and the number of short circuits in the short circuit welding may be gradually changed.

The second section 42 is a region that spans the first member W1 and the second member W2. In the second section 42, the welding operation is switched so that the first welding is performed on the first member W1 and the second welding is performed on the second member W2. Wherein in the first welding, at least short-circuit welding is performed, and in the second welding, at least pulse welding is performed.

Specifically, the first switching unit 38 selects the output of the pulse hybrid welding control unit 34, and performs pulse hybrid welding as the third welding in which the pulse welding period Tp for pulse welding and the short-circuit welding period Ts for short-circuit welding are alternately repeated a plurality of times. By performing pulse hybrid welding, abrupt changes in heat input when the welding current is changed can be suppressed.

When the pulse hybrid welding is performed during the first welding of the first member W1, the control unit 30 controls the operation of the welding unit 10 so that the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed during the pulse hybrid welding is greater than the ratio of the pulse welding period Tp during which the pulse welding is performed. In addition, when the pulse hybrid welding is performed during the second welding of the second member W2, the control unit 30 controls the operation of the welding unit 10 so that the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed during the pulse hybrid welding is smaller than the ratio of the pulse welding period Tp during which the pulse welding is performed.

In other words, when the first member W1 is subjected to the pulse hybrid welding, the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed in the pulse hybrid welding is larger than that when the second member W2 is subjected to the pulse hybrid welding, and when the second member W2 is subjected to the pulse hybrid welding, the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed in the pulse hybrid welding is smaller than that when the first member W1 is subjected to the pulse hybrid welding.

In this way, in the pulse hybrid welding, when the welding target area to be welded is the first member W1 having a small heat capacity, the ratio of the short-circuit welding period in which the short-circuit welding having a small heat input amount is performed can be made large, and when the welding target area to be welded is the second member W2 having a large heat capacity than the first member W1, the ratio of the pulse welding period in which the short-circuit welding having a large heat input amount is performed can be made large, so that the pulse hybrid welding can be performed under appropriate conditions.

In the first welding, control may be performed so that only short-circuit welding is performed, and pulse hybrid welding is not performed. In the pulse hybrid welding, the number of pulses in the pulse welding and the number of short circuits in the short circuit welding may be gradually changed.

In the second section 42, the control unit 30 controls the welding unit 10 so as to increase the welding current applied to the welding wire 15 before the welding gun 11 moving from the first member W1 toward the second member W2 crosses the boundary position Wb. In other words, the welding current applied when the welding gun 11 traverses the boundary position Wb from the first component W1 toward the second component W2 is greater than the welding current applied before the welding gun 11 traverses the boundary position Wb. Specifically, when the welding torch 11 traverses the boundary position Wb from the first member W1 toward the second member W2, an average welding current (also referred to as a set current) which is an average current that is a moving average of the welding current is larger than an average welding current applied before the welding torch 11 traverses the boundary position Wb. Thus, a welding current greater than the welding current applied to the welding wire 15 in the first section 41 is applied to the welding wire 15 in the second section 42.

Further, since the average welding current corresponds to the feeding amount of the welding wire 15, the feeding amount of the welding wire 15 can be increased to ensure the welding amount in the second section 42, which is the area of the step portion between the first member W1 and the second member W2 including the boundary position Wb, as compared with the first section 41 and the third section 43, and welding can be performed.

As described above, when the welding gun 11 moving from the first member W1 having a small heat capacity toward the second member W2 having a large heat capacity traverses the boundary position Wb, the current value applied to the welding wire 15 is increased, so that the feeding amount of the welding wire 15 at the boundary position Wb can be increased, and the pile height of the welding bead can be ensured. Thus, the step generated at the junction between the thin plate having a small heat capacity and the thick plate having a large heat capacity can be buried.

In the third section 43, the first switching unit 38 performs pulse welding by selecting an output of the pulse welding control unit 32 suitable for the second member W2 having a large heat capacity in the second welding for welding the second member W2.

In the third section 43, the first switching unit 38 may select the output of the pulse hybrid welding control unit 34 after the start of pulse welding, and perform pulse hybrid welding as third welding in which the pulse welding period Tp of pulse welding and the short-circuit welding period Ts of short-circuit welding are alternately repeated a plurality of times. By performing pulse hybrid welding, abrupt changes in heat input when the welding current is changed can be suppressed.

When the pulse hybrid welding is performed during the second welding of the second member W2, the control unit 30 controls the operation of the welding unit 10 so that the ratio of the pulse welding period Tp during which the pulse welding is performed during the pulse hybrid welding is greater than the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed. In this way, pulse hybrid welding can be performed under appropriate conditions. In the second welding, control may be performed so that only pulse welding is performed, and pulse hybrid welding is not performed. In the pulse hybrid welding, the ratio of the pulse welding period Tp in which the pulse welding is performed, the number of pulses in the pulse welding, the ratio of the short-circuit welding period Ts in which the short-circuit welding is performed, or the number of short-circuits in the short-circuit welding may be gradually changed.

The fourth section 44 is a region that spans the first member W1 and the second member W2. In the fourth section 44, the welding operation is switched so that the first welding is performed on the first member W1 and the second welding is performed on the second member W2. Wherein in the first welding, at least short-circuit welding is performed, and in the second welding, at least pulse welding is performed.

Specifically, the first switching unit 38 selects the output of the pulse hybrid welding control unit 34, and performs pulse hybrid welding as the third welding in which the pulse welding period Tp for pulse welding and the short-circuit welding period Ts for short-circuit welding are alternately repeated a plurality of times. By performing pulse hybrid welding, abrupt changes in heat input when the welding current is changed can be suppressed.

When the pulse hybrid welding is performed during the first welding of the first member W1, the control unit 30 controls the operation of the welding unit 10 so that the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed during the pulse hybrid welding is greater than the ratio of the pulse welding period Tp during which the pulse welding is performed. In addition, when the pulse hybrid welding is performed during the second welding of the second member W2, the control unit 30 controls the operation of the welding unit 10 so that the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed during the pulse hybrid welding is smaller than the ratio of the pulse welding period Tp during which the pulse welding is performed.

In other words, when the first member W1 is subjected to the pulse hybrid welding, the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed in the pulse hybrid welding is larger than that when the second member W2 is subjected to the pulse hybrid welding, and when the second member W2 is subjected to the pulse hybrid welding, the ratio of the short-circuit welding period Ts during which the short-circuit welding is performed in the pulse hybrid welding is smaller than that when the first member W1 is subjected to the pulse hybrid welding.

In this way, in the pulse hybrid welding, when the welding target area to be welded is the second member W1 having a small heat capacity, the ratio of the short-circuit welding period in which the short-circuit welding having a small heat input amount is performed can be made large, and when the welding target area to be welded is the second member W2 having a large heat capacity than the first member W1, the ratio of the pulse welding period in which the short-circuit welding having a large heat input amount is performed can be made large, so that the pulse hybrid welding can be performed under appropriate conditions.

In the first welding, control may be performed so that only short-circuit welding is performed, and pulse hybrid welding is not performed. In the pulse hybrid welding, the number of pulses in the pulse welding and the number of short circuits in the short circuit welding may be gradually changed.

Thus, the pulse welding, the pulse hybrid welding, and the short-circuit welding can be combined, and abrupt changes in heat input can be suppressed.

In the fourth section 44, the ratio of the short-circuit welding period Ts during which the short-circuit welding with a lower heat input than the pulse welding is performed is gradually increased in the pulse hybrid welding before the welding torch 11 traverses the boundary position Wb between the first member W1 and the second member W2 from the second member W2 with a larger heat capacity toward the first member W1 with a smaller heat capacity. In other words, the ratio of the number of short circuits in the pulse hybrid welding when crossing the boundary position Wb is larger than the ratio of the number of short circuits in the pulse hybrid welding before crossing the boundary position Wb.

As described above, the ratio of the number of short circuits when the welding torch 11 crosses the boundary position Wb is larger than the ratio of the number of short circuits before the welding torch 11 crosses the boundary position Wb, and the ratio of the number of short circuits is increased from before the welding torch 11 crosses the boundary position Wb to after the welding torch crosses the boundary position Wb, whereby the amount of stacked welding beads at the boundary position Wb can be ensured in a state of low heat input. Thus, the step generated at the junction between the thin plate having a small heat capacity and the thick plate having a large heat capacity can be buried.

Furthermore, the heat input of the short-circuit welding is low compared to the pulse welding. In the pulse hybrid welding in which a short-circuit welding period Ts in which short-circuit welding is alternately repeated and a pulse welding period Tp in which pulse welding is performed are repeated a plurality of times at a predetermined ratio, short-circuit welding with a low heat input has a cooling effect in the short-circuit welding period Ts. Therefore, heat input to the first member W1 can be suppressed, and burn-through can be suppressed. Further, during the pulse welding period Tp, the arc 16 expands to increase the width of the bead, and the droplet of the welding wire 15 regularly breaks away and transits to the bead formed by the pulse welding with high heat input, and the spatter is reduced.

In addition, by performing pulse hybrid welding during the spiral swinging operation, the welding speed can be increased without degrading the welding quality due to burn-through or the like. Next, a relation between the welding speed and the appearance of the weld bead will be described with reference to fig. 8 and 9.

Fig. 8 is a diagram of a comparative example, which shows a relationship between a welding speed and an appearance of a weld bead when pulse hybrid welding is performed without performing a spiral swing operation. In fig. 8, a photograph showing the appearance of the bead and a schematic drawing depicting the photograph of the appearance of the bead for visual easy understanding are shown.

As shown in FIG. 8, when the welding speed [ m/min ] was 0.3m/min or 0.4m/min, the scale pattern of the weld bead was continuously generated, and the appearance of the weld bead was good. On the other hand, if the welding speed [ m/min ] is increased to 0.5m/min, the generated bead may become uneven in scale, and the appearance of the bead may be deteriorated. For example, there is a tendency that: the faster the welding speed, the more the scale pattern of the bead gradually extends in the welding direction, and the finer the boundary line between the beads. Therefore, in the case of performing only pulse hybrid welding without performing the spiral swinging operation, the welding speed cannot be increased.

Fig. 9 is a diagram showing a relationship between a welding speed and an appearance of a bead when pulse hybrid welding is performed while performing a spiral swing operation. In fig. 9, a photograph showing the appearance of the bead and a schematic diagram depicting the appearance photograph of the bead so as to be easily understood visually are shown.

As shown in fig. 9, when the welding speed [ m/min ] was 0.7m/min, 0.8m/min, 0.9m/min, or 1.0m/min, scale marks of the weld bead were continuously generated, and the appearance of the weld bead was good. For example, even if the welding speed is increased, the shape of the bead scale pattern does not change greatly, and the boundary line between the beads can be clearly seen.

As such, it can be considered that: when pulse hybrid welding is performed while performing a spiral swing motion, a molten pool melted in pulse welding with high heat input is cooled by short-circuit welding with low heat input during the spiral swing motion, and a weld bead scale is easily generated. Therefore, the welding quality can be ensured, and the welding speed can be increased.

As described above, according to the arc welding method using the arc welding apparatus 1 according to the present embodiment, the joining quality between members having different heat capacities can be improved. Specifically, the first member W1 having a small heat capacity is subjected to at least short-circuit welding, and mainly short-circuit welding having a lower heat input than pulse welding, in other words, the ratio of the short-circuit welding period Ts of short-circuit welding having a low heat input is made large, whereby burn-through of the first member W1 can be suppressed. In addition, the second member W2 having a large heat capacity is subjected to at least pulse welding, and mainly pulse welding with high heat input is performed, in other words, the ratio of the pulse welding period Tp during which pulse welding with high heat input is performed is made large, whereby occurrence of insufficient penetration can be suppressed.

Further, according to the arc welding method using the arc welding apparatus 1 according to the present embodiment, even if the thicknesses of the welding target W at a plurality of welding sites are different from each other, the short-circuit welding, the pulse hybrid welding can be set for the welding target W composed of the components having different heat capacities based on the welding parameters (the welding current I, the welding voltage V, the feeding speed of the wire 15, the thickness of the welding target W, and the like) related to the heat input to the welding target W by adjusting the welding conditions. In this way, high-quality welding with high productivity, such as suppression of burn-through of the welded portion of the welding object W, can be realized with less spatter.

Modification of the present embodiment

As shown in fig. 10, the arc welding apparatus 1 performs welding while causing the welding gun 11 to perform a spiral swing motion in the welding direction. In the example shown in fig. 10, the welding wire 15 fed from the welding gun 11 is rotationally moved so as to rotate around the rotation center RC at a predetermined rotation frequency with a distance of a rotation radius r from the rotation center RC, which moves at a boundary position Wb between the first member W1 and the second member W2.

In the example shown in fig. 10, the distance r1 from the rotational position RC of the spiral track to the spiral track on the rear side in the welding direction is made shorter than the distance r2 from the rotational position RC of the spiral track to the spiral track on the front side in the welding direction without moving the welding gun 11 along the circular track. In this way, the arc 16 generated in the rear side in the welding direction can be made small, and the penetration can be suppressed, thereby ensuring the amount of pile of the weld bead.

In the example shown in fig. 10, the distance r2 from the rotational position RC of the spiral track to the spiral track on the front side in the welding direction is set to be the same as the rotational radius r, and the distance r1 from the rotational position RC of the spiral track to the spiral track on the rear side in the welding direction is set to be shorter than the distance r 2. For example, the distance r1 may be set to be the same length as the radius of rotation r, and the distance r2 may be set to be longer than the distance r 1.

(Other embodiments)

The embodiment may also employ the following constitution.

In the present embodiment, the heat capacity is made different by making the plate thickness of the second member W2 thicker than the plate thickness of the first member W1, but for example, the heat capacity may be made different by changing the material of the first member W1 and the material of the second member W2. For example, the first member W1 and the second member W2 may have the same plate thickness, the first member W1 may be formed of aluminum, and the second member W2 may be formed of a low carbon steel material. Thus, the first member W1 has a small heat capacity, and the second member W2 has a large heat capacity, which are different from each other. In other words, the heat capacity of the second member W2 is relatively large compared to the first member W1.

In the present embodiment, arc welding is performed in a state where the first member W1 and the second member W2 are in contact with each other, but the present invention is not limited to this embodiment. For example, the first member W1 and the second member W2 may be stacked in the thickness direction, and arc welding may be performed on the corners of the first member W1 and the second member W2.

Here, for example, if the plate thicknesses of the first member W1 and the second member W2 are the same, the heat capacity of the laminated portion of the first member W1 and the second member W2 is larger than that of the non-laminated portion. Therefore, the laminated portion of the two plates is assumed to be the second member, the non-laminated portion is assumed to be the first member, and short-circuit welding, pulse welding, and pulse hybrid welding may be performed in a switching manner as in the present embodiment.

In the present embodiment, pulse hybrid welding is performed in the first welding and the second welding, but the present invention is not limited to this method. For example, the first welding may be short-circuit welding, and the second welding may be pulse welding. The first welding may be short-circuit welding, and the second welding may be pulse hybrid welding. The first welding may be pulse hybrid welding, and the second welding may be pulse welding.

In the present embodiment, the welding torch 11 is caused to perform the spiral swinging motion, but the present invention is not limited to this embodiment. For example, the swinging motion may be performed by moving the welding torch 11 in the welding traveling direction while periodically swinging the welding torch 11 about the boundary position Wb so as to alternately traverse the boundary position Wb between the first member W1 and the second member W2 a plurality of times, and by moving the welding torch 11 in a zigzag manner. In this case, it is preferable that the welding torch 11 is periodically swung at an acute angle with respect to the boundary position Wb at a small amplitude during the swinging operation.

In the present embodiment, the radius r of the spiral track at the time of the spiral swinging operation is set to the same radius r on the first member W1 side and the second member W2 side, but may be different radii.

In the present embodiment, the welding wire 15 is fed so that the forward feeding and the reverse feeding of the welding wire are periodically repeated, but the present invention is not limited to this. For example, the wire 15 may be fed at a constant speed.

In the present embodiment, the ratio of pulse welding may be made larger at the front in the welding direction and the ratio of short-circuit welding may be made larger at the rear in the welding direction with reference to the center position of the spiral track during the swinging operation. In this way, the molten pool is formed by making the ratio of pulse welding with high heat input larger in the front of the welding direction, and the molten pool is cooled by making the ratio of short-circuit welding with low heat input larger in the rear of the welding direction. Thus, the weld bead can be made clear while preventing the weld object W from burning through.

Industrial applicability

As described above, the present invention is useful because it can exhibit a high practical effect of improving the joining quality between members having different heat capacities, and thus has a high industrial applicability.

Symbol description-

1. Arc welding device

10. Welding unit

11. Welding gun

13. Robot

15. Welding wire

30. Control unit

32. Pulse welding control part

33. Short circuit welding control part

34. Pulse hybrid welding control unit

40. Robot control unit

W welding object

W1 first part

W2 second part

Wb boundary position.

Claims (12)

1. An arc welding method for feeding a welding wire as a consumable electrode toward a welding object and generating an arc between the welding wire and the welding object to perform welding, characterized by comprising:

the welding object has a first member and a second member having a heat capacity larger than that of the first member,

The arc welding method comprises the following steps:

A step of welding while swinging the welding gun so as to alternately cross the boundary position between the first member and the second member a plurality of times; and

A step of switching welding operation so as to perform a first welding of the first member and a second welding of the second member during the swinging operation,

In the first welding, at least short-circuit welding is performed,

In the second welding, at least pulse welding is performed.

2. The arc welding method according to claim 1, wherein:

In at least one of the first welding and the second welding, a third welding is performed in which a short-circuit welding period in which the short-circuit welding is performed and a pulse welding period in which the pulse welding is performed are alternately switched a plurality of times.

3. The arc welding method according to claim 2, wherein:

The arc welding method comprises the following steps:

a step of making a ratio of the short-circuit welding period during which the short-circuit welding is performed in the third welding larger than a ratio of the pulse welding period during which the pulse welding is performed when the third welding is performed in the first welding; and

And a step of making a ratio of the pulse welding period during which the pulse welding is performed in the third welding larger than a ratio of the short-circuit welding period during which the short-circuit welding is performed when the third welding is performed in the second welding.

4. A method of arc welding according to claim 2 or 3, characterized in that:

the arc welding method comprises the following steps: in the second welding, before the welding gun traverses the boundary position from the second member toward the first member, switching is performed in the order of the pulse welding, the third welding, and the short-circuit welding.

5. The arc welding method according to any one of claims 2 to 4, characterized in that:

the arc welding method comprises the following steps: in the third welding, a step of gradually changing at least one of the number of pulses in the pulse welding and the number of shorts in the short-circuit welding.

6. The arc welding method according to any one of claims 1 to 5, characterized in that:

The welding current applied when the welding gun traverses the interface from the first component toward the second component is greater than the welding current applied before the welding gun traverses the interface.

7. The arc welding method according to any one of claims 2 to 6, characterized in that:

When the welding gun traverses the boundary position from the second member toward the first member, a ratio of a number of times of short-circuiting of the short-circuiting welding in the third welding is larger than a ratio of a number of times of short-circuiting of the short-circuiting welding in the third welding before the welding gun traverses the boundary position.

8. The arc welding method according to any one of claims 1 to 7, characterized in that:

the swinging motion is a spiral swinging motion moving along a spiral track,

At the boundary position, a distance from a center position of the spiral track to a spiral track on a rear side in the welding direction is shorter than a distance from the center position to a spiral track on a front side in the welding direction.

9. The arc welding method according to any one of claims 1 to 8, characterized in that:

in at least one of the first weld and the second weld, the welding wire is fed at a constant speed.

10. The arc welding method according to any one of claims 1 to 8, characterized in that:

In at least one of the first welding and the second welding, the forward feeding and the reverse feeding of the welding wire are periodically and repeatedly alternated to feed the welding wire.

11. The arc welding method according to any one of claims 2 to 10, characterized in that:

The swing motion is a spiral swing motion moving along a spiral trajectory, the third welding is performed, in the third welding, the short-circuit welding period in which the short-circuit welding is performed and the pulse welding period in which the pulse welding is performed are switched a plurality of times,

The ratio of the pulse welding period is made larger than the ratio of the short-circuit welding period in the front of the welding direction and the ratio of the short-circuit welding period is made larger than the ratio of the pulse welding period in the rear of the welding direction with respect to the center position of the spiral track.

12. An arc welding apparatus configured to feed a welding wire as a consumable electrode toward a welding object, and to generate an arc between the welding wire and the welding object to perform welding, the arc welding apparatus comprising:

the welding object has a first member and a second member having a heat capacity larger than that of the first member,

The arc welding apparatus includes a welding unit and a control part,

The welding unit performs welding while swinging the welding gun so as to alternately traverse the boundary position between the first member and the second member a plurality of times,

The control part controls the action of the welding unit,

During the swinging motion, the control part controls the motion of the welding unit so as to perform a first welding on the first member and a second welding on the second member,

In the first welding, at least short-circuit welding is performed,

In the second welding, at least pulse welding is performed.